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Calcimator

Slot Car Speed Calculator

Calculate actual and scale speed of slot cars from motor RPM, tire diameter, gear ratio, and scale.

Inputs

Results

Actual Speed (mph)

15.62

Scale Speed (mph)

499.8

Tire Surface Speed (mph)15.6
Laps/Min (30ft track)45.8
How to Use This Calculator
  1. Enter Motor RPM, Tire Diameter (mm), and Gear Ratio.
  2. Set Scale, HO (1:87), and 1:32.
  3. Adjust 1:24 as needed.
  4. Review Actual Speed (mph) and Scale Speed (mph).
  5. Use Tire Surface Speed (mph) and Laps/Min (30ft track) to inform your decision.

How the result changes with Gear Ratio

Gear RatioActual Speed (mph)Scale Speed (mph)
1.924.66789.1
4.1511.29361.3
6.856.84218.9
9.15.15164.8

What each input means

Motor RPM
Motor rotational speed in revolutions per minute
Tire Diameter (mm)
Outer diameter of the drive tires in millimeters
Gear Ratio
Ratio between motor gear and axle gear (e.g., 3:1)
Scale
Slot car scale for scale speed calculation

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Motor RPM = 20000, Tire Diameter (mm) = 20, Gear Ratio = 3, Scale = 2 = 4 input(s) provided
  2. Calculate Actual Speed
    Actual Speed
    15.62 = 15.62
  3. Calculate Scale Speed
    Scale Speed
    499.8 = 499.8
  4. Calculate Tire Surface Speed
    Tire Surface Speed
    15.6 = 15.6
  5. Calculate Laps/Min
    Laps/Min
    45.8 = 45.8

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